As an example of a conventional liquid crystal display, FIG. 9 and FIG. 10 illustrate a liquid crystal display described in Japanese patent laid-open publication No. 10-221715. FIG. 9 is a plan view showing a portion of an active matrix substrate in such liquid crystal display. FIG. 10 is a cross sectional view taken along the line A—A of FIG. 9.
As shown in FIG. 10, an active matrix substrate 50 comprises an insulating substrate 51 made, for example, of glass and the like, a gate insulating film 52 formed on the insulating substrate 51, a passivation film 53 formed on the gate insulating film 52, an interlayer insulating film 54 formed on the passivation film 53, and pixel electrodes 55 which are formed in a matrix on the interlayer insulating film 54.
Also, as shown in FIG. 9, gate lines 56 and data lines 57 are disposed on the periphery of each of the pixel electrode 55. The gate lines 56 and the data lines 57 are perpendicular to each other, and surround each of the pixel electrodes 55. As shown in FIG. 10, each of the gate lines 56 is formed on the insulating substrate 51, and each of the data lines 57 (not shown in FIG. 10) is formed on the gate insulating film 52.
As shown in FIG. 9, a thin film transistor (TFT) 58 as a switching element is disposed in the proximity of each of the intersections between the gate lines 56 and the data lines 57. The thin film transistor 58 is electrically coupled to the pixel electrode 55 via a contact hole 59 which is formed in the interlayer insulating film 54.
A gate electrode of the thin film transistor 58 is coupled with the gate line 56, and the thin film transistor 58 is driven and controlled by a signal applied to the gate electrode via the gate line 56. Also, a drain electrode of the thin film transistor 58 is coupled with the data line 57, and a data signal is inputted to the drain electrode via the data line 57.
Further, as shown in FIG. 10, a control electrode 60 is formed on the interlayer insulating film 54, between adjacent pixel electrodes 55 and over the gate line 56. The control electrode 60 is formed in the same layer as that of the pixel electrodes 55.
FIG. 10 also shows an opposing substrate 64 which opposes to the active matrix substrate 50. The opposing substrate 64 comprises an insulating substrate 61, a color filter 62 formed on the insulating substrate 61, and an opposing electrode 63 formed on the color filter 62. The opposing substrate 64 is disposed such that the opposing electrode 63 and the pixel electrodes 55 oppose to each other.
On each of the opposing surfaces of the active matrix substrate 50 and the opposing substrate 64, there is disposed an alignment layer (not shown in the drawing). Also, there is provided a liquid crystal layer 65 which is held between the alignment layers on the active matrix substrate 50 and on the opposing substrate 64. Also, spacers (not shown in the drawing) are disposed between the active matrix substrate 50 and the opposing substrate 64 to keep a predetermined thickness of the liquid crystal layer 65. Further, there is formed a seal (not shown in the drawing) around the liquid crystal layer 65 for preventing liquid crystal molecules from leaking outside.
In the conventional liquid crystal display mentioned above, the control electrode 60 is disposed between adjacent pixel electrodes 55. The control electrode 60 is provided to avoid occurrence of so-called reverse tilt. The reverse tilt occurs when an electric field caused by the potential difference between the gate line 56 and the pixel electrodes 55 intrudes into the liquid crystal layer 65, and alignment direction of liquid crystal molecules partly differs from a predetermined direction.
However, in a manufacturing technology of liquid crystal display, it is considerably difficult to form the control electrodes 60 in the same layer as that of the pixel electrodes 55.
Also, as shown in FIG. 10, the space between mutually adjacent pixel electrodes 55 is not large and, therefore, the width of the control electrode 60 can not be so large. Further, when the control electrode 60 is to be formed in such narrow space between adjacent pixel electrodes 55, there is a high possibility that the control electrode 60 contacts one or both of the adjacent pixel electrodes 55.
In addition, it is necessary to provide some gaps 67 between the control electrode 60 and the pixel electrodes 55, in order to physically separate between the control electrode 60 and the pixel electrodes 55. When such gaps 67 are provided between the control electrode 60 and the pixel electrodes 55, the electric field produced by the potential difference between the gate line 56 and the pixel electrodes 55 is not shielded completely by the control electrode 60. Therefore, such electric field passes through the gaps 67, and extends horizontally along the pixel electrodes 55 into the liquid crystal layer 65. In this way, there is a possibility that so-called lateral leak of electric field designated by a reference numeral 68 is produced.
Such lateral leak of electric field 68 causes reverse tilt of liquid crystal molecules in the liquid crystal layer 65, and as a result causes disclination.